1. Field of the Invention
The present invention relates to an image forming apparatus that forms an image on a transfer medium (a sheet on which an image is to be recorded) and includes a sheet outputting mechanism for outputting the transfer medium to outside the image forming apparatus.
2. Description of the Related Art
An exemplary configuration of existing image forming apparatuses is described below with reference a laser printer, an example of a multi-color image forming apparatus.
FIG. 15 is a cross-sectional view of an exemplary configuration of an existing image forming apparatus. Components of the image forming apparatus shown in FIG. 15 are described in detail below. FIG. 16 illustrates interface signals between an engine control unit 201 (not shown in FIG. 15) that forms an image in the image forming apparatus shown in FIG. 15 and a controller 202 (not shown in FIG. 15).
As shown in FIG. 16, a serial command transmission signal line 203 is used for serially transmitting a command from the controller 202 to the engine control unit 201. A serial status transmission signal line 204 is used for serially transmitting status data from the engine control unit 201 to the controller 202 in response to the command. A reference vertical synchronizing signal line 205 is used for transmitting a reference vertical synchronizing signal (hereinafter referred to as a “TOP signal”) from the engine control unit 201 to the controller 202. A Y horizontal synchronizing signal line 206 is used for transmitting a yellow horizontal synchronizing signal from the engine control unit 201 to the controller 202. An M horizontal synchronizing signal line 207 is used for transmitting a magenta horizontal synchronizing signal from the engine control unit 201 to the controller 202. A C horizontal synchronizing signal line 208 is used for transmitting a cyan horizontal synchronizing signal from the engine control unit 201 to the controller 202. A K horizontal synchronizing signal line 209 is used for transmitting a black horizontal synchronizing signal from the engine control unit 201 to the controller 202. A Y image data signal line 210 is used for transmitting a yellow image data signal from the controller 202 to the engine control unit 201. An M image data signal line 211 is used for transmitting a magenta image data signal from the controller 202 to the engine control unit 201. A C image data signal line 212 is used for transmitting a cyan image data signal from the controller 202 to the engine control unit 201. A K image data signal line 213 is used for transmitting a black image data signal from the controller 202 to the engine control unit 201.
FIG. 17 is a timing diagram illustrating signal timings for the TOP signal, the horizontal synchronizing signals, and the image data when a full color mode is selected.
Upon receipt of a print operation start command from a host computer (not shown), the controller 202 submits a print operation start command to the engine control unit 201 via the serial command transmission signal line 203. Upon receipt of the print operation start command, the engine control unit 201 starts a print operation and transmits a status message indicating that it has started a print operation to the controller 202 via the serial status transmission signal line 204.
When the print operation starts, the engine control unit 201 starts operating photoconductor drums 5Y, 5M, 5C, and 5K, an intermediate transfer belt 12, and scanner units 10Y, 10M, 10C, and 10K shown in FIG. 15 to prepare for forming images of respective colors. As shown in FIG. 17, when the preparation is completed, the engine control unit 201 outputs a TOP signal 301 to the controller 202 via the reference vertical synchronizing signal line 205 in order to provide vertical synchronization for a first color. In this example, images of a yellow color component, a magenta color component, a cyan color component, and a black color component are sequentially formed in this order. The controller 202 outputs yellow image data 303 to the engine control unit 201 via the Y image data signal line 210 in synchronization with the TOP signal 301 and a Y horizontal synchronizing signal 302 output from the engine control unit 201.
The engine control unit 201 primarily transfers, to the intermediate transfer belt 12, a visible image formed on the photoconductor drum 5Y on the basis of the yellow image data 303 delivered from the controller 202. The engine control unit 201 outputs, to the controller 202, a timing at which the yellow toner image transferred onto the intermediate transfer belt 12 passes through the lowest point of the magenta conductive drum 5M. The controller 202 outputs magenta image data 305 to the engine control unit 201 in synchronization with that timing. At that time, the controller 202 outputs the magenta image data 305 to the engine control unit 201 after a predetermined time period T1 (indicated by a reference numeral 304 shown in FIG. 17) has elapsed so that the yellow toner image is located at the lowest point of the magenta conductive drum 5M. The engine control unit 201 performs control so that a primary transfer unit located at the lowest point of the magenta conductive drum 5M primarily transfers the visible image formed on the magenta conductive drum 5M to the intermediate transfer belt 12 exactly at the position of the yellow toner image. Similar operations are performed for cyan and black toner images. At that time, the operations are performed so that the images of the four colors exactly overlap. That is, as shown in FIG. 17, the controller 202 starts generating cyan image data 307 and black image data 309 after predetermined time periods T2 (indicated by a reference numeral 306) and T3 (indicated by a reference numeral 308) have elapsed from the time the TOP signal is output, respectively. In addition, the engine control unit 201 forms images corresponding to the image data on the intermediate transfer belt 12.
As noted above, in the color laser printer, under the control of the engine control unit 201, an image forming unit forms electrostatic latent images using imaging light beams generated on the basis of image signals transmitted from the controller 202. The image forming unit then develops the electrostatic latent images into visible images, which are overlapped and transferred. Thus, a color visible image is formed. The image forming unit transfers this color visible image onto a transfer medium 2 shown in FIG. 15. Subsequently, the image forming unit fixes the color visible image onto a transfer medium 2.
As shown in FIG. 15, the image forming unit includes the photoconductor drums 5Y, 5M, 5C, and 5K for stations of the respective colors arranged in parallel. The image forming unit further includes injection charging units 7Y, 7M, 7C, and 7K serving as primary charging units. Furthermore, the image forming unit includes developing units 8Y, 8M, 8C, and 8K, toner cartridges 11Y, 11M, 11C, and 11K, the intermediate transfer belt 12, a sheet feeder unit, a transfer unit, and a fixing unit 13.
The photoconductor drums (photosensitive members) 5Y, 5M, 5C, and 5K are each composed of an aluminum cylinder having an organic photoconductive layer applied on the outer periphery thereof. The photoconductor drums 5Y, 5M, 5C, and 5K are rotated by driving forces transferred from driving motors (not shown). As shown in FIG. 15, the driving motors rotate the photoconductor drums 5Y, 5M, 5C, and 5K in a counterclockwise direction in accordance with the image forming operation. The scanner units 10Y, 10M, 10C, and 10K emit exposure light beams to the photoconductor drums 5Y, 5M, 5C, and 5K, respectively, to selectively expose the surfaces of the photoconductor drums 5Y, 5M, 5C, and 5K. Thus, electrostatic latent images are formed.
The image forming unit includes four injection charging units 7Y, 7M, 7C, and 7K in the corresponding stations for charging yellow (Y), magenta (M), cyan (C), and black (K) photoconductor drums, respectively. In addition, the injection charging units 7Y, 7M, 7C, and 7K include sleeves 7YS, 7MS, 7CS, and 7KS, respectively. The injection charging units 7Y, 7M, 7C, and 7K provide a primary charging mechanism.
The image forming unit further includes four developing units 8Y, 8M, 8C, and 8K in the corresponding stations so as to develop yellow (Y), magenta (M), cyan (C), and black (K) images, respectively. In addition, the developing units 8Y, 8M, 8C, and 8K include sleeves 8YS, 8MS, 8CS, and 8KS, respectively. The developing units 8Y, 8M, 8C, and 8K are removably mounted on the body of the image forming apparatus.
The intermediate transfer belt 12 is in contact with the photoconductor drums 5Y, 5M, 5C, and 5K. When a color image is formed, the intermediate transfer belt 12 rotates in a clockwise direction in FIG. 15. The intermediate transfer belt 12 is rotatingly driven by the rotations of the photoconductor drums 5Y, 5M, 5C, and 5K so that visible images are transferred onto the intermediate transfer belt 12. In addition, when an image is formed, a transfer roller 9a, which is described below, contacts the intermediate transfer belt 12 so as to pinch the transfer medium 2 and convey the transfer medium 2. Thus, a color visible image formed on the intermediate transfer belt 12 is in contact with the transfer medium 2 and is transferred onto the transfer medium 2 at one time.
When the color visible image formed on the intermediate transfer belt 12 is transferred onto the transfer medium 2, the transfer roller 9a is in contact with the intermediate transfer belt 12. However, after a print operation is completed, the transfer roller 9a is moved away from the intermediate transfer belt 12 to a position 9b. 
The fixing unit 13 fixes the transferred color visible image while conveying the transfer medium 2. As shown in FIG. 15, the fixing unit 13 includes a fuser roller 14 that applies heat to the transfer medium 2 and a pressure roller 15 that urges the transfer medium 2 against the fuser roller 14. The fuser roller 14 and the pressure roller 15 are hollow inside so as to allow incorporation of a heater 16 and a heater 17, respectively. That is, the transfer medium 2 bearing the color visible image is conveyed by the fuser roller 14 and the pressure roller 15. At the same time, by applying heat and pressure to the transfer medium 2, the toner is fixed on the surface of the transfer medium 2.
A cleaning unit 21 removes residual toner from the photoconductor drums 5Y, 5M, 5C, and 5K and the intermediate transfer belt 12. Residual toner left on the photoconductor drums 5Y, 5M, 5C, and 5K after the visible toner images are transferred to the intermediate transfer belt 12 is stored in a cleaner container (not shown) by the cleaning unit 21. Alternatively, residual toner left on the intermediate transfer belt 12 after the four-color visible image formed on the intermediate transfer belt 12 is transferred to the transfer medium 2 is stored in a cleaner container (not shown) by the cleaning unit 21.
A flapper solenoid 23 switches between a face-up (FU) tray 24 and a face-down (FD) tray 25 having a longer conveying path than the FU tray 24 so that the transfer medium 2 having the fixed visible image is output to the selected tray. After the transfer medium 2 is output onto either one of the FU tray 24 and the FD tray 25, the image forming operation is completed. As used herein, the term “face-up (FU)” refers to an output of the transfer medium 2 with the surface having a formed image facing upward, and the term “face-down (FD)” refers to an output of the transfer medium 2 with the surface having a formed image facing downward.
When the transfer medium 2 is normally conveyed, the printer having such a configuration temporarily stops the conveyance of the transfer medium 2 after a predetermined time period has elapsed from the time that a sensor 19 detects the passage of the leading edge of the transfer medium 2 (see FIG. 18A). Note that the sensor 19 also functions as a sensor for detecting a paper jam. At that time, as shown in FIG. 18B, the transfer medium 2 is curved by a roller 28. Thereafter, the printer starts driving the roller 28 in synchronization with the movement of the image formed on the intermediate transfer belt 12 to resume conveyance of the transfer medium 2.
An exemplary control operation of a transfer medium performed by the engine control unit 201 is described next with reference to FIGS. 19 and 20.
FIG. 19 is a flow chart illustrating a sequence of detecting the size of the transfer medium 2 using the sensor 19 of the engine control unit 201. As used herein, the term “detected size of a transfer medium” refers to the length of a transfer medium in a direction in which the transfer medium is conveyed. The sensor 19 and the engine control unit 201 function as a size detecting unit that detects the size of the transfer medium 2. The size detecting unit is described later.
As shown in FIG. 19, the engine control unit 201 determines the time to resume conveyance of the transfer medium 2 in a state shown in FIG. 18B (step S501). When the time to resume conveyance of the transfer medium 2 is reached, the engine control unit 201 starts a timer count (step S502). The transfer medium 2 is then conveyed. When the sensor 19 detects the passage of the trailing edge of the transfer medium 2 (step S503) (see FIG. 18C), the engine control unit 201 stops the timer count. The engine control unit 201 computes the size of the transfer medium 2 on the basis of a predetermined curved value, a distance between the sensor 19 and the roller 28, and a timer count value (step S504). A variety of computing methods can be employed in accordance with the required precision and efficiency. Since these computing methods are well known to those skilled in the art, description is not provided here. If it is determined at step S505 that the difference between the size of the transfer medium 2 computed at step S504 and a size specified by the controller 202 is within a predetermined range, the engine control unit 201 completes the size detection sequence. However, if the difference is not within the predetermined range, the processing of the engine control unit 201 proceeds to step S506. At step S506, the engine control unit 201 moves the transfer roller 9a away from the intermediate transfer belt 12 and sends a message indicating that the size of the transfer medium 2 does not match the specified size to the controller 202. Thus, the controller 202 determines that a print failure occurred. In this case, the transfer medium 2 is output to a paper output tray specified by the controller 202. This operation is described in more detail below with reference to FIG. 20.
In the above-described image forming apparatus having the mechanism of detecting an actual size of the conveyed transfer medium 2 and a plurality of paper output ports, the control of outputting the transfer medium 2 when the specified size does not match the actual size of the transfer medium 2 is described next with reference to FIG. 20.
The engine control unit 201 detects a timing of the conveyed transfer medium 2 passing the sensor 19 and determines the size of the transfer medium 2 using the detection result (step S601). This process is similar to that shown in FIG. 19. If the computed size of the transfer medium 2 matches the size specified by the controller 202, the engine control unit 201 determines that a paper output port specified by the controller 202 is one that can output the transfer medium 2. Accordingly, the engine control unit 201 outputs the transfer medium 2 to the paper output port specified by the controller 202 (steps S602 and S610).
However, if the computed size of the transfer medium 2 does not match the specified size, the engine control unit 201 performs the following control (steps S602 and S603).
The engine control unit 201 determines whether the specified paper output port is the FD tray 25 or the FU tray 24 (step S603). If the FU tray 24 is selected (step S604), the engine control unit 201 switches the flapper solenoid 23 to the FU tray 24 (step S607) so as to output the transfer medium 2 onto the FU tray 24 (step S608).
However, if the FD tray 25 is selected, the engine control unit 201 compares the detected size of the transfer medium 2 with a maximum distance between rollers in a conveying path towards the FD tray 25 (step S604). If the size of the transfer medium 2 is greater than the maximum distance between the rollers, the transfer medium 2 can be output to the FD tray 25. However, if the maximum distance between the rollers is greater than the size of the transfer medium 2, the transfer medium 2 cannot be conveyed and is left in the image forming apparatus. Therefore, it is determined that the transfer medium 2 cannot be output to the FD tray 25. If it is determined that the transfer medium 2 can be output to the FD tray 25, the engine control unit 201 switches the flapper solenoid 23 to the FD tray 25 (step S605) so as to output the transfer medium 2 to the FD tray 25 (step S606). However, if the size of the transfer medium 2 is smaller than the maximum distance between the rollers, and therefore, the transfer medium 2 cannot be delivered to the FD tray 25, the engine control unit 201 switches the flapper solenoid 23 to the FU tray 24 so as to forcibly output the transfer medium 2 to the FU tray 24 (steps S604, S607, and S608).
As noted above, if the specified size of the transfer medium 2 is different from the actually detected size and if the detected size is so small that the transfer medium 2 cannot be output to the FD tray 25, the engine control unit 201 automatically outputs the transfer medium 2 to the FU tray 24. Thus, the transfer medium 2 that would cause a print failure can be output to outside the image forming apparatus without remaining inside the image forming apparatus. Thus, ease of use can be improved.
A control method for the case when a paper output option unit is installed on the image forming apparatus and the specified size is different from the actual size of the transfer medium 2 is described next.
The paper output option unit exchanges information with the engine control unit 201 through the controller 202. Accordingly, a method is described in which the controller 202 determines a paper output port that can output the transfer medium 2 so that print and conveyance operations are smoothly performed.
FIG. 21 is a flow chart illustrating a sequence of the operations performed by the engine control unit 201 including an operation for detecting the size of the transfer medium 2. FIG. 22 is a flow chart illustrating control of outputting the transfer medium 2 performed by the controller 202. FIGS. 23 and 24 are timing diagrams illustrating a relationship between the size of the transfer medium 2 and a switching operation between paper output ports of the paper output option unit. FIG. 25 is a cross-sectional view of the image forming apparatus on which the paper output option unit having a staple function or a booklet maker function is installed. FIG. 26 is a block diagram illustrating a relationship among the engine control unit 201, the controller 202, and a paper output option control unit (neither is shown in FIG. 25).
An exemplary structure of an image forming apparatus on which a paper output option unit 30 is installed is described next with reference to FIG. 25. When the paper output option unit 30 is installed, a printer engine has no paper output ports. Only an FU1 paper output port (FU tray) 24 and an FU2 paper output port 31, which are paper output ports of the paper output option unit 30, are provided. A flapper solenoid 29 in the paper output option unit 30 switches whether the transfer medium 2 is output to the FU1 paper output port 24 or the FU2 paper output port 31. The transfer medium 2 is output from the printer engine and is delivered to the paper output option unit 30. Thereafter, the transfer medium 2 is output to one of the FU1 paper output port 24 and the FU2 paper output port 31 by a paper output option control unit.
As shown in FIG. 26, the engine control unit 201 exchanges information 1001 and 1002 with a paper output option control unit 214 through the controller 202. The paper output option control unit 214 receives a command from the controller 202 so as to control the paper output option unit 30.
As shown in FIG. 21, the engine control unit 201 determines whether the paper output option unit 30 is installed or not (step S701). If the paper output option unit 30 is not installed, the engine control unit 201 performs control in a manner similar to that described in FIG. 20 (step S705). However, if the paper output option unit 30 is installed, the engine control unit 201 detects the size of the transfer medium 2, as illustrated in FIG. 19 (step S702). Then, the engine control unit 201 makes a determination shown at step S602. If the result is “NO”, the processing proceeds to step S610. If the detected size does not match the specified size, the engine control unit 201 sends a status message indicating that the specified size does not match the detected size and the detected size itself to the controller 202 (steps S703 and S704).
As shown in FIG. 22, the paper output option control unit 214 sends the size data of a transfer medium that can be output from the FU1 paper output port 24 and the size data of a transfer medium that can be output from the FU2 paper output port 31 to the controller 202 in advance (step S1201). The controller 202 determines whether it has received the status message indicating that the specified size does not match the detected size and the detected size itself from the engine control unit 201. If the controller 202 has received the status message, the processing proceeds to step S1203 (steps S1202 and S1203).
The controller 202 determines whether the size of the transfer medium 2 is one that can be output from a paper output port specified by a host computer. That is, the controller 202 compares the size of the transfer medium 2 detected by the engine control unit 201 with the size of a transfer medium that can be output from the specified paper output port (the size received from the paper output option control unit 214). Thus, the controller 202 determines whether the transfer medium 2 can be output to the specified paper output port (step S1203). If the size of the transfer medium 2 detected by the engine control unit 201 is within the range of the size of a transfer medium that can be output from the specified paper output port, the controller 202 directly outputs the transfer medium 2 to the specified paper output port. That is, the controller 202 submits a paper output port selection command including the size data of the transfer medium 2 (step S1204). Subsequently, if the controller 202 has not received the size data of the transfer medium 2 at step S1202 and receives the size data from the engine control unit 201 during the paper output (step S1205), the controller 202 performs a process similar to that at step S1203. That is, the controller 202 determines whether the transfer medium 2 can be output to the current paper output port (step S1206). If the paper output cannot be performed (step S1207), the controller 202 sends a user a message indicating that the transfer medium 2 is left in the paper output option unit 30 using a graphic user interface (GUI) on a display unit (not shown) (step S1208). If, at step S1203, the size of the transfer medium 2 detected by the engine control unit 201 is not within the range of the size of a transfer medium that can be output from the specified paper output port, the controller 202 performs a process at step S1209. That is, the controller 202 compares the size of the transfer medium 2 detected by the engine control unit 201 with the size of a transfer medium that can be output from another paper output port (the size received from the paper output option control unit 214). Thus, the controller 202 searches for another paper output port (step S1209). If a paper output port from which the transfer medium 2 can be output is found, the controller 202 submits a paper output port switch command including the size data of the transfer medium 2 to the paper output option control unit 214 so that the paper output option control unit 214 can output the transfer medium 2 using that paper output port (step S1210). However, if no paper output ports from which the transfer medium 2 can be output are found, the controller 202 sends the user a message indicating that the paper output cannot be performed and the transfer medium 2 is left in the printer engine (i.e., a jam occurred) using a GUI on a display unit (not shown) (steps S1211 and S1212). The paper output option control unit 214 receives the paper output port selection command at step S1204 or receives the paper output port switch command at step S1210 so as to switch the flapper solenoid 29 to the specified paper output port. Subsequently, the paper output option control unit 214 outputs the transfer medium 2.
FIGS. 23 and 24 are timing diagrams for detecting a transfer medium when the above-described processes illustrated in FIGS. 21 and 22 are performed. FIG. 23 is a timing diagram for the case when the size of the transfer medium 2 is small. In many cases, the process is performed in accordance with this timing diagram. FIG. 23 corresponds to the processes at steps S1201, S1204, S1205, to “END” or the processes at steps S1203, S1209, S1210, to “END” shown in FIG. 22. FIG. 24 is a timing diagram for the case when the size of the transfer medium 2 is very large compared with that shown in FIG. 23. FIG. 24 corresponds to the processes at steps S1204, S1205, S1206, to “END” or the process at step S1207 shown in FIG. 22. As shown in FIG. 24, if the size of a transfer medium specified in the paper output port selection command is an unconveyable size, the paper output option control unit 214 unconditionally determines that a jam has occurred.
Several documents describe techniques related to the above-described known technologies (refer to, for example, Japanese Patent Laid-Open Nos. 2003-26365, 2003-40468, and 2001-88370).
As described in FIG. 24, in a known technology for detecting the size of a transfer medium, when a very long (a large sized) transfer medium is conveyed, a timing at which the engine control unit 201 sends the size of the transfer medium to the paper output option unit 30 may be delayed. In such a case, since the size of the transfer medium is large (very long), the transfer medium may be input to the paper output option unit 30 before the sensor 19 completes the size detecting operation. In this case, if the transfer medium has a size that cannot be conveyed in the paper output option unit 30, the conveyance of the transfer medium must be forcibly stopped in the paper output option unit 30 (i.e., a conveyance failure like a jam occurs). In addition, when a plurality of transfer media are continuously conveyed and these transfer media are delivered to a conveyance unit for duplex printing in the image forming apparatus, the conveying path of the plurality of transfer media is complicated. In such a case, even when the controller 202 or the paper output option control unit 214 receives information indicating that the size of the transfer medium does not match the size of a transfer medium that can be output to a paper output port and the size itself, it may be difficult to determine to which transfer medium in the conveying path the received information corresponds. The above-described known technologies do not address these issues.